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Determination of the Exposure Dosage for Positive Photoresists

IP.com Disclosure Number: IPCOM000060927D
Original Publication Date: 1986-Jun-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 23K

Publishing Venue

IBM

Related People

Chesnutt, RB: AUTHOR [+2]

Abstract

This method involves the use of high pressure liquid chromatography to isolate the photoactive component of the photoresist in both its unexposed and exposed forms. This quantitative technique can pinpoint the amount of exposure necessary to obtain complete pattern development, providing a simple and fast analytical method which replaces subjective trial and error experiments. In general, positive resists contain various organic solvents, a phenolic resin, and a photoactive component. Upon exposure, the photoactive component is converted into an aqueous soluble material. This reaction sequence, ignoring the ketene intermediate, is shown in the figure. Of main importance is the drastic solubility difference between the unexposed and exposed photoactive component.

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Determination of the Exposure Dosage for Positive Photoresists

This method involves the use of high pressure liquid chromatography to isolate the photoactive component of the photoresist in both its unexposed and exposed forms. This quantitative technique can pinpoint the amount of exposure necessary to obtain complete pattern development, providing a simple and fast analytical method which replaces subjective trial and error experiments. In general, positive resists contain various organic solvents, a phenolic resin, and a photoactive component. Upon exposure, the photoactive component is converted into an aqueous soluble material. This reaction sequence, ignoring the ketene intermediate, is shown in the figure. Of main importance is the drastic solubility difference between the unexposed and exposed photoactive component. This is the basis for being able to analyze a resist sample for the amount of exposure it has received by high pressure liquid chromatography. The exposed photoactive component, being of organic nature, is retarded on the organic reverse phase column, but the exposed photoactive component is water- soluble and elutes much faster, resulting in total separation of its two forms. Wafers were coated with positive photoresist using routine process conditions, blanket exposed for various times, dissolved in tetrahydrofuran, and analyzed by high pressure liquid chromatography to observe the degree of photoactive component conversion with exposure tim...